it's definitely unclear to me how doable that is; bmeurer is _also_ worried about adding more %_ intrinsics (at a high level, there's some discussion to be had between the language team and the runtime/compiler folks; we

caitp: I believe that an inlined CreateDataProperty and this desugaring is one way to do it, but given that bmeurer's worried about the use of %_ArgumentsLength(i), some higher-level rethinking might be the way to improve performance here